Construction of B-doped g-C3N4/MoO3 photocatalyst to promote light absorption and Z-scheme charge transfer

Constructing highly efficient semiconductor photocatalysts with batch production is essential for the large-scale applying semiconductor photocatalysts in the fields of environmental remediation and energy conversion. In this study, we used melamine as the precursor and boric acid as the dopant to prepare high-yield B-doped g-C3N4 (BCN), and composited it with the wide band gap semiconductor of MoO3 to construct BCN-MoO3 hetero-junctions. B doping causes the valence band of g-C3N4 to shift up, which not only reduces the band gap for light absorption, but also causes the top of the valence band of CN to be close to the bottom of the conduction band of MoO3, which is conducive to the formation of Z-scheme heterostructures between BCN and MoO3. As such, the current BCN-MoO3 composite has effective visible light photocatalytic activity for rhodamine (RhB), methyl orange (MO) and tetracycline (TC). The results showed that the BCN-MoO3 composite with a 15 % mass ratio of MoO3 had the best degradation performance, which was characterized by the complete degradation of RhB within 24 min, while the degradation rate of the control sample of 15 % CN-MoO3 catalyst without B doping was only 66 % within 40 min. A direct Z-type charge transfer model was established by measuring the energy level position, X-ray photoelectron spectroscopy analysis and radical scavenging experiments. Superoxide radicals play vital role in photocatalytic degradation, and the role of holes and hydroxyl radicals cannot be ignored.